Method for manufacturing a filter capable of trapping carcinogens and toxic chemicals

ABSTRACT

A method for manufacturing a filter is introduced. Firstly, a polyurethane material including a urethane-based main chain having a repeat unit of the formula, (R—NH—COO—R—O—NH) n , with a plurality of contaminants absorbed around the urethane-based main chain is provided. Then, an extraction is performed to remove the contaminants from the urethane-based main chain so as to reveal a plurality of absorption sites for trapping cyanides, phenols, or polynuclear aromatic compounds.

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This is a continuation-in-part of U.S. application Ser. No.09/682,257, filed Aug. 10, 2001, and which is included herein byreference. The present application claims priority under 35 U.S.C. Â§120 to U.S. patent application Ser. No. 09/252,334, filed Feb. 18, 1999and now issued as U.S. Pat. No. 6,273,095, which in turns claimspriority under 35 U.S.C. Â§ 119(e) to U.S. Provisional ApplicationSerial No. 60/093330, entitled SAFE CIGARETTE FILTER, filed Jul. 20,1998.

BACKGROUND OF INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a method for manufacturing afilter capable of removing cyanides and polynuclear aromatic compoundsfrom cigarette smoke, and more specifically, to a method formanufacturing a filter capable of removing cyanides, phenols, andpolynuclear aromatic compounds from air.

[0004] 2. Description of the Prior Art

[0005] People begin smoking cigarettes for a variety of reasons. Smokinghas been portrayed as being heroic, cool and as enhancing sexual appeal.For some people, smoking also serves to soothe tension, anxiety, orloneliness. However, as is commonly known, cigarette smoke contains theaddictive compound nicotine. Addiction to nicotine makes it verydifficult for smokers to stop smoking cigarettes, even though manyrealize that smoking will adversely affect their health.

[0006] The serious negative health effects of smoking are generallycaused by chemicals in tobacco smoke other than nicotine. Among theseare polynuclear aromatic compounds, which are carcinogens suspected tocause or contribute to a variety of cancers. The formation ofpolynuclear aromatic compounds in cigarette smoke is the result ofincomplete combustion of the cigarette due to short burning residenttime. Furthermore, polynuclear aromatic compounds harm not only smokers,but also the surrounding environment and people who inhale them assecond-hand smoke. Furthermore, tobacco smoke also contains cyanides, ahighly toxic compound which causes adverse health effects in smokers andthose inhaling second-hand smoke.

[0007] The tobacco industry has attempted to alleviate the problemscaused by polynuclear aromatics and cyanides by incorporating filtersinto cigarettes to remove these compounds when a smoker inhales. Thesefilters are typically made of cellulose-based materials. The filters areeffective in removing some of the toxic chemicals from tobacco smoke,but a substantial amount still passes through the filter. Consequently,there exists a need for improving filters for cigarettes and othertobacco products, which are more efficacious in removing toxic andcarcinogenic chemicals from tobacco smoke. Moreover, to encourage use ofsuch a filter, the filter should not interfere with those aspects ofsmoking which smokers desire, including the taste and nicotine contentof the smoke.

SUMMARY OF INVENTION

[0008] It is therefore an objective of the present invention to providea method for manufacturing a filter capable of removing cyanides,phenols, and polynuclear aromatic compounds from air.

[0009] It is another objective of the present invention to provide amethod for manufacturing a filter capable of selectively removespolynuclear aromatic compounds and low molecular weight compoundincluding mono-aromatic compounds and cyanides from tobacco smoke, whilepermitting most of the nicotine and flavor-enhancing molecules in thesmoke to pass through. Because of this, people smoking tobacco productswho use the filter of the present invention may enjoy the smokingexperience, but with less exposure to the dangerous components oftobacco smoke.

[0010] According to the present invention, a method for manufacturing afilter capable of removing cyanides, phenols, or polynuclear aromaticcompounds from air is provided. Firstly, a polyurethane materialincluding a urethane-based main chain having a repeat unit of theformula, (R—NH—COO—R—O—NH)_(n), with a plurality of contaminantsabsorbed around the urethane-based main chain is provided. Then, anextraction is performed to remove the contaminants from theurethane-based main chain so as to reveal a plurality of absorptionsites for trapping cyanides, phenols, or polynuclear aromatic compounds.

[0011] In one aspect of the present invention, the polyurethane filtercomprises a tubular body with a proximal and a distal end. The tubularbody is formed out of middle-density cellular polyurethane foam. Thefoam is pre-treated to increase the number of available absorption sitesfor absorbing polynuclear aromatic compounds, pernicious mono-aromaticcompounds, and cyanides. When used with a cigarette having aconventional filter, the polyurethane foam filter having an uncompressedvolume of about 2 cubic centimeters absorbs about 60% of the polynucleararomatic compounds and cyanide contained in cigarette smoke whichcontact the filter, but permits about 75% of the contacting nicotine inthe smoke to pass through.

[0012] In another embodiment, a polyurethane foam filter of the presentinvention is substantially substituted for a conventional cigarettefilter and is incorporated into the body of the cigarette as part of themanufacturing process. In this embodiment, a polyurethane foam filter,which prior to incorporation into the cigarette has an uncompressedvolume of about 2-cubic centimeters, absorbs at least 74% of thepolynuclear aromatic hydrocarbons contacting the filter in thecigarette, but permits about 75% of the nicotine contacting the filterto pass through. In another embodiment, a similarly sized polyurethanefoam filter of the present invention is completely substituted for aconventional cigarette filter and absorbs at least 90% of thepolynuclear aromatic hydrocarbons which pass through the filter.

[0013] In another aspect of the present invention, there is provided animproved filter for removing carcinogenic and toxic compounds fromtobacco smoke. The invention comprises a pre-treated polyurethane foambody which absorbs 30-45% of contacting total polynuclear aromaticcompounds per cubic centimeter of uncompressed polyurethane foammaterial forming the filter, but which permits more than 88% of thecontacting nicotine to pass through unabsorbed per cubic centimeter ofpolyurethane foam material. The improved filter having these propertiesmay be incorporated into a cigarette body, a cigar or a pipe body.

[0014] In another aspect of the present invention, there is provided apre-treated polyurethane foam filter which absorbs in aggregate 60%-90%of 2-methylnaphthalene, acenaphthylene, acenaphthene, dibenzofuran,fluorene, phenantherne, anthracene, carbazole, fluoranthene, pyrene,benzo(a) anthracene and chrysene in tobacco smoke passing through thefilter per 2 cubic centimeters of uncompressed foam used to make thefilter.

[0015] In another aspect of the present invention, there is provided amethod of making a safer cigarette. The method comprises providing amiddle-density cellular polyurethane foam (PUF), which may then beformed into a cylindrical body to form a filter. The PUF filter is thenpre-treated by cleaning to increase the polynuclear aromatic compoundand cyanide absorption sites. Alternately, the pre-treating step mayoccur before PUF filter is shaped into the cylindrical body. Thecylindrical body is incorporated into a cigarette as a filter such thatwhen the cigarette is lit, smoke will pass through the PUF filter priorto being inhaled by a smoker.

[0016] These and other objectives of the present invention will no doubtbecome obvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment, which isillustrated in the multiple figures and drawings.

BRIEF DESCRIPTION OF DRAWINGS

[0017]FIG. 1 is a cross-sectional view of a cigarette incorporating thefilter of the present invention into the body of the cigarette.

[0018]FIG. 2 illustrates extracted polyurethane foam having absorptionsites for trapping cyanides and phenols via hydrogen bonds.

[0019]FIG. 3 is a cross-sectional view of a filter of the presentinvention incorporated into a cigarette holder that may be attached anddetached from cigarettes.

[0020]FIG. 4 illustrates the comparison of polynuclear aromaticemissions (in ng) of cigarette smoke from a filterless cigarette, aconventional cigarette with a filter, and a cigarette with a PUF filter.

[0021]FIG. 5 is analytical results of experiment 1.

[0022]FIG. 6 is analytical results of experiment 2.

[0023]FIG. 7 is analytical results of experiment 4.

[0024]FIG. 8 is a summary of percentage of total polynuclear aromaticsabsorbed by a PUF filter.

DETAILED DESCRIPTION

[0025] Referring to FIG. 1, there is shown a cigarette 10 incorporatinga polyurethane foam (PUF) filter 35 of the present invention. Althoughillustrated and described in the context of a tobacco cigarette, itshould be understood by those of skill in the art that the filter of thepresent invention might be readily incorporated in a mask or otherfiltering device that is applied to filter out pollutants or poisonousgas from air. Moreover, although the filter of the present invention isdescribed as having a tubular or cylindrical shape, it should beappreciated by those of skill in the art that the filters of the presentinvention may take other shapes, including square, rectangular,spherical, and the like.

[0026] As shown in FIG. 1, the cigarette 10 comprises a cylindrical body12 formed from a paper product, which is wrapped around tobacco 20. Thecigarette 10 has a distal end 14 and a proximal end 16. In this respect,the cigarette 10 may be any conventional cigarette known to those ofskill in the art, such as those made and sold today by the tobaccoindustry. The cigarette 10 may also incorporate a conventional filter 25near the proximal end 16 thereof. The conventional filter 25 is used incigarettes sold today, such as cellulose-based filters, but may bereduced in size when used in conjunction with the PUF filter 35 of thepresent invention, as described below.

[0027] Polyurethane foam (PUF) has been used by United StatesEnvironmental Protection Agency to trap polynuclear aromatic compounds,polychlorinated biphenyls, dioxins/furans, and the like, from air withreasonably high efficiency. These compounds have an affinity forpolyurethane, and tend to be absorbed onto the surface of polyurethane.However, the polyurethane foam cannot efficiently absorb low molecularweight compounds, including cyanides, phenols, and aromatic compoundswith a single aromatic ring. Accordingly, the present invention makesthe polyurethane foam be pre-treated to form the PUF filter 35 capableof effectively removing not only the polynuclear aromatic compounds butalso the low molecular weight compounds from cigarette smoke or air.

[0028] As shown in FIG. 1, the PUF filter 35 is incorporated at aproximal end 16 by being wrapped with a paper product. Preferably, thecigarette 10 also incorporates a portion of the conventional filter 25,and the PUF filter 35 is positioned proximal to the conventional filter25 at the proximal end 16. When this two-filter combination is used, theconventional filter 25 will function to protect the PUF filter 35 fromburning when the tobacco is completely combusted. In this respect, it ispreferred that the conventional filter 25 have a diameter approximatelythat of the cigarette body 12, and a length of from about 1 mm to about4 mm, and more preferably from about 2 mm to about 3 mm. As statedabove, the conventional filter 25 may be made of cellulose-basedmaterials. However, other types of materials known to those of skill inthe art may be used in place of the conventional filter 25 to protectthe PUF filter 35, provided that the materials are compatible withpolyurethane foams. Moreover, in some embodiments, it may be desirableto eliminate the conventional filter 25, and use only the PUF filter 35at the proximal end 16 of the cigarette 10.

[0029] As described above, the PUF filter 35 is formed from thepolyurethane foam, which has extensive cellular structure and ispreferably selected from middle-density polyurethane foam having adensity of from about 0.01 to about 0.05 grams per milliliter. Morepreferably, the polyurethane foam used will have a density of from about0.02 to about 0.04 grams per milliliter. However, it should beunderstood by those of skill in the art that any polyurethane foam witha cellular structure and appropriate density that permits cigarettesmoke to pass through may be used with the present invention, providedthat it conforms to the teachings herein. One kind of polyurethane foamfound suitable for use in the present invention may be purchased fromSan Antonio Foam Fabricator, Product No. NA-85. This foam has a cellularstructure and a density of 0.0302 grams per milliliter. Additionally,the PUF filter 35 could also be formed from polyurethane fibers, whichcould achieve the goal of filtering out low molecular weight compounds,as well as polyurethane foams.

[0030] The PUF filter 35 may vary in size and dimension as desired bythe cigarette manufacturer. Preferably, the PUF filter 35 hasapproximately the same diameter as the cigarette in which it isincorporated and a length similar to conventional filters used today forcigarettes. This length may average from about 1 to 2.5 centimeters.Furthermore, because the beneficial effects of the present inventionresult from the polyurethane foam absorbing the harmful compounds,providing a larger polyurethane foam filter will tend to increase thetotal percentage of these compounds absorbed. As described in moredetail below, the polyurethane foam formed into the filter having avolume of two cubic centimeters has been shown to successfully absorbabout 75% of the polynuclear aromatic compounds passing through it.

[0031] As mentioned above, the present invention makes the polyurethanefoam be pre-treated to form the PUF filter 35 capable of effectivelytrapping not only the polynuclear aromatic compounds but also the lowmolecular weight compounds, including cyanides, phenols, and aromaticcompounds with a single aromatic ring. One method that has been shownuseful to achieve this is Soxhlet extraction, which cleans thepolyurethane foam and therefore increases the number of absorption sitesfor trapping cyanides, phenols, and polynuclear aromatic compounds. Inthe Soxhlet extraction, a solvent containing 6% ether in hexane isevaporated from a solvent reservoir. The solvent vapor is then condensedinto a chamber containing the polyurethane foam to be treated. Thepolyurethane foam in the chamber is gradually immersed in the condensedsolvent until it is totally immersed. Most of the contaminants on or inthe polyurethane foam will be extracted into the solvent. The solvent inthe chamber is then siphoned through a tube down to the solventreservoir at the bottom. The solvent evaporated out of the solventreservoir is always pure and free from contaminants from thepolyurethane foam. Therefore, only contaminant-free solvent is condensedinto the chamber and all contaminants from the polyurethane foamaccumulate in the reservoir. The solvent in the chamber is siphonedapproximately once every hour for 16 hours. After the Soxhletextraction, excess solvent is removed from the polyurethane foam byblowing it to dryness in nitrogen.

[0032] Before the polyurethane foam is pre-treated, the polyurethanefoam originally comprises a urethane-based main chain and a plurality ofcontaminants absorbed by the urethane-based main chain. Usually, theurethane-based main chain has a repeat unit of theformula:(R—NH—COO—R—O—NH)_(n), wherein the R group is an aliphaticchain, such as n-octyl, and the R group is an aromatic group, such astolyl. In addition, the contaminants absorbed by the urethane-based mainchain include phenols, such as 6-tert-butyl-2,4-dimethylphenol andbutylated methyl phenol, tinuvin, monomers, dimers, oligomers,4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione, and so on.Furthermore, it is observed that the NH moieties of the urethane-basedmain chain are originally occupied by 6-tert-butyl-2,4-dimethylphenol,butylated methyl phenol and another unknown phenol, while the R groupand the R group are originally absorbed by tinuvin, monomers, dimers,oligomers, and 4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione.

[0033] It should be noticed that after the polyurethane foam isextracted by use of the Soxhlet extraction, those unwanted contaminantsare removed from the polyurethane foam, thus revealing theurethane-based main chain having a plurality of absorption sites.Referring to FIG. 2, FIG. 2 illustrates extracted polyurethane formhaving absorption sites for trapping cyanides and phenols via hydrogenbonds. As shown in FIG. 2, the urethane-based main chain of thepolyurethane foam is revealed after the polyurethane foam is pre-treatedby the Soxhlet extraction. Additionally, as shown in FIG. 2, thenitrogen atom of the NH moiety has a lone pair electron that can absorba hydrogen atom of cyanides or phenols due to hydrogen bonds, so thatthe NH moieties function as absorption sites for trapping cyanides andphenols. Furthermore, after the removal of the contaminants, the R groupand the R group are available for absorbing polynuclear aromaticcompounds via van der Waals attraction that is molecular attractingforce between neutral and non-polar organic portions. Therefore, the Rgroup and the R group are regarded as absorption sites for absorbingpolynuclear aromatic compounds. As a result, the polyurethane foam thatis pre-treated by the Soxhlet extraction can trap not only polynucleararomatic compounds but also the low molecular weight compounds,including cyanides, phenols, and aromatic compounds with a singlearomatic ring. However, most of the nicotine, which is a substitutedpyridine, and some small volatile molecules contributing to the smoke'sflavor in the smoke still can pass the pre-treated polyurethane foam, sothat a pleasant sensation of a smoker may not be decreased.

[0034] Other methods suitable to pre-treat the polyurethane foam andtherefore increase its polynuclear aromatic compound and toxic compoundabsorption sites may include extraction using solvents other than 6%ether in hexane, such as methylene chloride, hexane, light hydrocarbonbased solvents, and mixtures of the foregoing. Furthermore,supercritical fluid extraction, steam distillation, hot solventextraction and any other suitable organic extraction technique may alsobe used.

[0035] Referring to FIG. 3, there is shown as an alternative embodimentof the PUF filter of the present invention, where the PUF filter isincorporated into a cigarette holder 50 which can be removably attachedto a conventional cigarette 100. As shown in FIG. 3, the cigarette 100comprises a tubular body composed of a paper product wrapped aroundtobacco 120. A conventional filter 125 may be incorporated into thetubular body at a proximal end 116, but this is not required. Thecigarette holder 50 has a generally tubular body 55, which extends froma distal end 54 to a proximal end 56, and as shown in FIG. 3, tapers toa smaller diameter beginning at a point 58 to form a smaller diametermouthpiece opening 65 at the proximal end 56. The cigarette holder 50may take a variety of other forms, as may be aesthetically pleasing orto provide ergonomic benefits. Furthermore, the holder 50 may be formedfrom any of the variety of materials known to those of skill in the artto be useful for manufacture of cigarette holders, such as metals andplastics. The holder 50 may also vary in length, diameter andappearance, as desired by its manufacturer to provide for desiredaesthetic and ergonomic properties.

[0036] For purposes of the present invention, the holder 50 merelyprovides structure to encompass a polyurethane foam filter and providean airway channel so that cigarette smoke inhaled by a smoker must passthrough the polyurethane foam filter. For the holder 50, such an airwaychannel is defined by a lumen 60, which extends from the proximal end 56to the distal end 54.

[0037] The lumen 60 has a larger inner diameter at the distal end 54,and is proportioned to receive the proximal end of a conventionalcigarette. Preferably, the lumen 60 is dimensioned to snugly fit over aconventional cigarette, such that a cigarette inserted into the lumen 60will be held firmly in place, but may be removed with minimal effort bya person. Incorporated into the lumen 60 is a polyurethane foam (PUF)filter 35 of the present invention. Preferably, the PUF filter 35 hasbeen pre-treated to increase the number of absorption sites forabsorbing polynuclear aromatic compounds and cyanides, as describedabove. The PUF filter 35 should have a diameter to fill the entirely ofthe lumen 60, such that any cigarette smoke which passes through thelumen 60 to the mouthpiece opening 65 must pass through the PUF filter35. This may be accomplished by forming the PUF filter 35 to have anuncompressed diameter slightly greater than that of the lumen 60, andthen slightly compressing the PUF filter 35 so that it fits snugly inthe lumen 60.

[0038] In this manner, polynuclear aromatic compounds, cyanides, andmono-aromatic compounds which contact and bind to the absorption sitesin PUF filter 35 will be removed from cigarette smoke as they passthrough the PUF filter 35. Because these compounds are removed from thesmoke prior to being inhaled by a smoker, they should not adverselyaffect the smoker's health, and should not adversely affect bystander'shealth through second-hand smoke. However, as described previously, mostof the nicotine and flavor-enhancing molecules present in the smoke willpass through the PUF filter 35 to mouthpiece opening 65. Thus a pleasantsensation of a smoker may not be decreased.

[0039] The selective absorption properties of the polyurethane foam ofthe present invention are demonstrated in the following experimentalexamples.

[0040] Experimental Examples

[0041] A set of cylindrical PUF filters was cut from a sheet of NA-85polyurethane foam. Each cylindrical PUF filter had an outside diameter(O.D.) of about 1 cm and a height of 1 inch (2.54 cm), and therefore inan uncompressed state had a volume of about 2 cubic centimeters. The PUFfilters were then pre-treated to increase polynuclear aromatic andcyanide absorption sites by Soxhlet extraction as described above with6% ether in hexane for 16 hours. The PUF filters were then blown todryness using nitrogen until all of the solvent was removed.

[0042] One of the PUF filters was slightly compressed and then insertedinto clean 6.7 inch long and 0.8 cm inside diameter (I.D.) glass tubingwith 1.8 cm tapered end. The filter end of a Dorall Full Flavor Premium™cigarette was inserted into the other end of the glass tubing. Becausethe O.D. of PUF filter was slightly larger than the I.D. of the glasstubing, the PUF filter fit snugly in the tubing and all tobacco smokepassing through the glass tubing passed through the PUF filter. Teflontape was wrapped around the filter end of the cigarette and glass tubingto seal them together. All of the Dorall cigarettes used in the studywere from the same package.

[0043] The glass tubing was then connected horizontally to an inlet of a100 mL impinger manufactured by Ace Glassware. The impinger used in thisstudy was designed to trap polynuclear aromatics, cyanide and tarpassing through the PUF filter.

[0044] All the trapped polynuclear aromatics, cyanide and tar in theimpinger would have been inhaled by a smoker if the cigarette had beensmoked. The outlet of the impinger was connected to a hand-pump (Mityvac#OB61, Neward Enterprises, Cucamonga, Calif.). Each press of thehand-pump pumped approximately 30-40 mL of air through the cigarette tosimulate an inhalation by an average smoker. The impinger was thenimmersed in liquid argon and the cigarette was lit. Continuous pumpingwas then applied to the hand pump to suck the air through the cigarette.Cigarette smoke went through the PUF filter, impinger, and hand-pumpbefore venting into a fume hood. The hand-pump was continuously pumpedby hand until the cigarette had 4 mm of length left. The approximatesampling time was one minute.

[0045] After sampling, the impinger was filled with 70 mL of methylenechloride to dissolve the tar collected and left overnight. Afterwards,the methylene chloride was poured into a vial. The impinger was thenrinsed with methylene chloride to capture any tar remaining in theimpinger, and the rinse was poured into the same vial. The methylenechloride solution was concentracted down to 20 mL prior to gaschromatography and mass spectroscopy (GC/MS) analysis. A 4 mL sample ofthe methylene chloride solution was blown down with nitrogen to removeall methylene chloride and the residue or tar was weighed to fivedecimal places. The tar was weighed twice: one at five minutes after thefirst weighing and the second in the next day. The average of the tarweights is reported in FIG. 5.

[0046] The PUF filter used in the experiment was removed from the glasstubing. The PUF filter was then Soxhlet extracted using methylenechloride and the extract was concentrated to 5 mL before GC/MS analysis.One milliliter of the extract was used to measure the weight of tar bythe method mentioned above.

[0047] This experiment was repeated as described above, except that inthe second experiment the cigarette was completely burned. Theconventional cigarette filter burned slightly before end of thesampling.

[0048] The same procedure as the first experiment was performed fourmore times with the following changes to the protocol:

[0049] Experiment 3 was with a conventional filtered cigarette andwithout a PUF filter,

[0050] Experiment 4 was with a partially filtered cigarette and a PUFfilter,

[0051] Experiment 5 was with an unfiltered cigarette and without a PUFfilter,

[0052] Experiment 6 was with a PUF filter, but without a cigarette(laboratory blank).

[0053] In Experiment 4, 75% of the regular cigarette filter was removedand replaced with a PUF filter without tearing the paper holding thecigarette filter. The remaining 25% of the regular cigarette filtersegregated the cigarette from PUF filter to prevent burning of the PUFfilter during this experiment.

[0054] Results

[0055] No compounds were detected in the laboratory blank in either theimpinger and PUF filter (Experiment 6).

[0056]FIG. 4 shows a table comparing the polynuclear aromatics and tartrapped in the impinger while (1) using the cigarette with only aconventional cigarette filter; (2) using a partially filtered cigarettewith only a PUF filter; and (3) using the cigarette without any filter.As shown in FIG. 4, the PUF filter of the present invention issignificantly better than regular cigarette filters in removing toxicpolynuclear aromatics such as 2-methylnaphthalene, acenaphthylene,acenaphthene, dibenzofuran, fluorene, phenanthrene, anthracene,carbazole, fluoranthene, pyrene, benzo(a)anthracene and chrysene. Thisis demonstrated from comparing the weight of polynuclear aromaticcompounds found in the impinger when a conventional filter was used tothose found when the PUF filter was used. However, the nicotine andcotinine (oxidation product of nicotine) emissions from the cigarettewith PUF filter are roughly the same as a cigarette with the regularcigarette filter.

[0057] The percentage of polynuclear aromatics and tar removed in theother experiments using the PUF filter are listed in FIG. 5 to FIG. 7and summarized in FIG. 8. In those experiments where a 2 cubiccentimeter PUF filter is used in conjunction with a regular cigarettefilter, the PUF filter of the present invention removed about 60% ofpolynuclear aromatic compounds in cigarette smoke which contacted it, or30% per cubic centimeter of uncompressed foam material. Furthermore, thePUF filter permitted about 75% of the nicotine in cigarette smoke whichcontacted the PUF filter to pass through. In those embodiments in whichabout 75% of the regular filter of a cigarette was replaced with the PUFfilter, the PUF filter removed about 74% of polynuclear aromaticcompounds contacting it, or about 37% per cubic centimeter ofuncompressed foam material, but still permitted about 75% of thenicotine in cigarette smoke to pass through.

[0058] As noted above, a PUF cylindrical body having a volume of 2 cubiccentimeters in its uncompressed state was slightly compressed andinserted into the experimental apparatus to function as a filter. InExperiment 4, this PUF filter removed 74% of the polynuclear aromaticcompounds when used without a complete regular filter (75% of theregular filter removed), compared to only 60% when a complete regularfilter was used as in Experiment 1. This may be due to the fact thatthere are significant amounts of glycerol triacetate embedded in mostregular cigarette filters. It was observed that the amount of glyceroltriacetate found in each experiment was approximately the same as thatof nicotine. The glycerol triacetate emitted during these experimentsmay be trapped by the PUF filters. The trapped glycerol triacetate wouldoccupy many of the absorption sites on the PUF filter, which would beotherwise available for polynuclear aromatics. Therefore, with acomplete regular cigarette filter, the efficacy of the PUF filtertrapping polynuclear aromatics was reduced, compared to when used withonly a partial (25%) regular cigarette filter. In view of these results,it is expected that the percentage of polynuclear aromatic compoundsabsorbed by the PUF filter would increase from 74% to about 80-90% per 2cubic centimeters of uncompressed PUF starting material, if the PUFfilter is used without any conventional cigarette filter, or if theamount of glycerol triacetate in regular cigarette filter is reduced.

[0059] Three more experiments were performed to determine the efficiencyof PUF filters in removing cyanide from cigarette smoke. Theseexperiments were performed in the same manner as the first experiment.However, instead of 70 mL of methylene chloride to dissolve tar trappedin the impinger by liquid argon, 37 mL of 0.25 N sodium hydroxide wasadded to impinger to rinse and convert trapped inorganic cyanidecompounds to cyanide anion, which was then analyzed by ionchromatography. For a cigarette with conventional filter but without PUFfilter, 660 micrograms of total cyanide were found in the 37 mL impingerrinsing solution. This was from the smoke that would have been inhaledby the smoker if the cigarette had been smoked. However, for a cigarettewith both regular filter and PUF filter, 250 micrograms of total cyanidewere found in the 37 mL impinger rinsing solution. For a blank, an unlitcigarette with regular filter but without PUF filter was used. For theblank, cyanide was not found at the detection limit of 3.7 micrograms inthe 37 mL impinger rinsing solution. These experiments indicate thatapproximate 62% of totalcyanide in cigarette smoke passing through thePUF filter was removed by a PUF filter of the present invention.

[0060] Because the PUF filter used in this study are made from mediumdensity polyurethane foam, the pressure drop across the PUF filter ismuch lower than regular cigarette filter. Most smokers familiar with aconventional cigarette filter may not be familiar with a filter whichhas a low pressure drop. Consequently, they may inhale larger quantitiesof smoke at the beginning. Therefore, smokers may either be informed ofthe lower pressure drop, or use a PUF filter as an additional filterafter the regular cigarette filter. In the latter way, the PUF filtermay be inserted in a cigarette holder and then a cigarette with regularfilter is inserted into the cigarette holder before smoking.

[0061] Although this invention has been described in terms of certainpreferred embodiments, other embodiments will be apparent to those ofordinary skill in the art in view of the disclosure herein are alsowithin the scope of this invention. Accordingly, the scope of theinvention is intended to be defined only by reference to the appendedclaims.

What is claimed is:
 1. A method for manufacturing a filter comprising:providing a polyurethane material comprising a urethane-based main chainhaving a repeat unit of the formula, (R—NH—COO—R—O—NH)_(n), with aplurality of contaminants absorbed around the urethane-based main chain;and performing an extraction to remove the contaminants from theurethane-based main chain so as to reveal a plurality of absorptionsites for trapping cyanides, phenols, or polynuclear aromatic compounds;wherein the R group is an aliphatic chain and the R group is an aromaticgroup.
 2. The method of claim 1 wherein each of the absorption sites isselected from the group consisting of the NH moiety, the R group, andthe R group.
 3. The method of claim 2 wherein the nitrogen atom of theNH moiety has a lone pair electron for binding the phenols and thecyanides via hydrogen bonds.
 4. The method of claim 2 wherein the Rgroup and the R group absorb the polynuclear aromatic compounds via vander Waals attraction.
 5. The method of claim 2 wherein the NH moiety isoriginally occupied by the contaminants comprising phenols.
 6. Themethod of claim 5 wherein the phenols comprise6-tert-butyl-2,4-dimethylphenol and butylated methyl phenol.
 7. Themethod of claim 2 wherein the R group and the R group are originallyoccupied by the contaminants comprising tinuvin, monomers, dimers,oligomers, and 4,4,5,6-tetramethyltetrahydro-1,3-oxazin-2-thione.
 8. Themethod of claim 1 wherein the R group comprises n-octyl.
 9. The methodof claim 1 wherein the R″ group comprises tolyl.
 10. The method of claim1 wherein the extraction is a Soxhlet extraction.
 11. The method ofclaim 10 wherein the Soxhlet extraction uses a solvent containing 6%ether in hexane to extract the contaminants from the polyurethanematerial for revealing the urethane-based main chain.
 12. The method ofclaim 10 wherein the Soxhlet extraction uses a solvent comprisingmethylene chloride, hexane, light hydrocarbon based solvents, ormixtures of the foregoing to extract the contaminants from thepolyurethane material for revealing the urethane-based main chain. 13.The method of claim 1 wherein the extraction is a supercritical fluidextraction, a steam distillation, a hot solvent extraction, or anorganic extraction.
 14. The method of claim 1 further comprising dryingthe urethane-based main chain for forming the filter.
 15. The method ofclaim 1 wherein the polyurethane material is polyurethane foam orpolyurethane fiber.
 16. The method of claim 1 wherein the polynucleararomatic compounds comprise 2-methylnaphthalene, acenaphthylene,acenaphthene, dibenzofuran, fluorene, phenanthrene, anthracene,carbazole, fluoranthene, pyrene, benzo(a)anthracene, and chrysene. 17.The method of claim 1 wherein the polyurethane material has a density ofbetween about 0.01 g/ml to about 0.05 g/ml.